There is growing popularity of computer devices and portable electronic devices each of which has both a display function and an input function and each of which allows an operation to be performed by operating it in such a manner as to touch a displayed image. Such an electronic device employs a display panel called a touch panel (or a touchscreen). In the mainstream of touch panels are capacitive touch panels, and also in the mainstream is a system in which a change in capacitance of a sensor electrode is detected and this change in capacitance is converted into an input signal.
For example, Japanese Laid-Open Patent Publication No. 2010-140369 discloses a capacitive touch panel including: a transparent substrate; a first electrode pattern formed on one surface of the transparent substrate, the first electrode pattern being formed by a transparent conductive film, the first electrode pattern having a plurality of X electrodes arranged along a row-wise direction and in rows; an intermediate insulating layer formed over the first electrode pattern, and a second electrode pattern formed over the intermediate insulating layer, the second electrode pattern being formed by a transparent conductive film, the second electrode pattern having a plurality of Y electrodes arranged along a column-wise direction and in columns, the second electrode pattern forming a matrix with the first electrode pattern. Putting this touch panel on top of a display panel such as a liquid crystal panel can constitute an external touch panel. However, merely integrating a touch sensor panel with a display panel ends up causing the resulting panel to be thick and heavy.
On the other hand, a touch panel called an internal (in-cell) touch panel is structured such that a touch sensor unit is fabricated into a color filter substrate or an element substrate. For example, Japanese Laid-Open Patent Publication No. 2011-053620 discloses, as an example of a sensor-containing type, a method for manufacturing a substrate for use in a display device with a touch panel, the method including: forming a touch sensor layer on one surface of a substrate; forming a protecting layer that protects the touch sensor layer; and forming a color filter layer over the other surface of the substrate, wherein the color filter layer is formed after the protecting layer is formed.
The touch panel disclosed in Japanese Laid-Open Patent Publication No. 2010-140369 does not have a protective film on an output wiring (metal wiring) connected to an electrode pattern formed by a transparent conductive film, and as such, it is structured such that the output wiring is broken due to a flaw and/or corroded by moisture or the like. Further, since the output wiring made from metal is formed after the electrode pattern formed by the transparent conductive film is formed, processing of the output wiring by dry etching causes the electrode pattern formed by the transparent conductive film to be etched. Further, processing of the output wiring by wet etching raises such a problem that the occurrence of electrolytic corrosion makes it impossible to make contact between the electrode pattern and the output wiring.
The method for manufacturing a substrate for use in a display device with a touch panel as disclosed in Japanese Laid-Open Patent Publication No. 2011-053620 provides a touch sensor unit with a protective film; however, the protective film is merely intended to protect the electrodes and/or wirings of the touch sensor, and is incorporated into the substrate for use in a display device in such a structure as not to be useful at all for the element substrate or the color filter substrate.
However, merely integrating a touch sensor panel with a display panel ends up causing the resulting panel to be thick and heavy. In view of this, there has been proposed a system (in-cell type) in which a touch sensor function is fabricated into one of two substrates constituting a display panel. In such a case, however, flexible printed wirings are attached to both an element substrate and an opposite substrate to which a touch sensor function has been added. This makes it necessary to fix the two substrates while keeping them thin.